Plant images

Plant biology

Spiny burr grass produces several stems from the base which are branched, hairless and somewhat flattened, particularly at the base. They are either erect or spreading and ascending.

Roots are formed at basal nodes when in contact with soil.

Leaves

Leaves of spiny burr grass are wide and smooth but sometimes twisted and wrinkled. They have fine serrations and flattened sheaths growing to a length of 20 cm and a width of 5-8 mm. The ligule is a narrow membrane fringed with hairs 1-1.5 mm long

Flowers

Flowers of spiny burr grass have a spike-like panicle 3-8 cm long consisting of up to 40 burrs and are often partially enclosed in a leaf sheath.

The burr is yellow to green, 3-7 mm in diameter (excluding the spines) and comprising of one to four florets.

Spines are purple-tinged, spreading or reflexed, slender but broadened at the base. They are sharply pointed, finely barbed and rigid.

Growth and lifecycle

Spiny burr grass is spread by water, animals, fodder, clothing and machinery. The seed contains barbed spines on the burr which attach to wool, fur, clothing, bags and other fibrous materials.

Seedbank propagule persistence

Spiny burr grass can produce up to 1,000 seeds per plant with some seeds remaining dormant for up to three years.

While some plants may survive a mild winter to produce a small crop of burrs, this species is essentially an annual. A mature plant produces seeds for only one year. The weed germinates in spring or summer with burr produced from December to April. Most plants die in autumn.

Preferred habitat

Spiny burr grass prefers temperate sub-humid and semi-arid regions where it grows well on low-fertility, sandy, well drained soils. It establishes readily on disturbed sites in the 250-500 mm annual rainfall belt. The weed has some tolerance to frost and low temperatures.

Distribution

Spiny burr grass is well established in the dry farmlands of the Victorian and South Australian Mallee and in irrigated areas along the Murray River in both states.

Growth calendar

The icons on the calendar below represent the times of year for flowering, seeding, germination, the dormancy period of Spiny burr grass and also the optimum time for treatment.

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Flowering

Seeding

Germination

Dormancy

Treatment

Impact

Impact on ecosystems and waterways

Spiny burr grass grows well on disturbed road edges and infests neglected areas and summer crops. The weed forms tussocks of up to 30 cm high and 60 cm across.

It grows in open, dry sandy conditions and is a pioneer plant of disturbed sandy soils. It also grows well under irrigation. Disturbance enhances invasiveness and can cause displacement of desirable grass species.

Agricultural and economic impacts

Spiny burr grass does not establish readily in pastures.

The burrs can become badly tangled in wool, lowering its value and making sheep difficult to handle. This can result in additional costs to handle burr-infested stock. Spines from the plant can easily puncture the skin of animals and affect the value of the hides. The weed is also a contaminant in
dried fruit and may infest lucerne hay.

Social value and health impacts

The spines of spiny burr grass can easily puncture the skin of animals and has the potential to injure fauna. Spines may also injure humans.Burrs are present for much of the year. The plant does not pose any restrictions to human movement except when burrs are present.

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